Show only chosen month for two different date fields. But the month field is created from one of the date fields

[arunqlik2view]

Hello All,

I have 2 dates fields "Date" and " TransactionDate". Now, I have a month field created from "date" column. So when I choose month from the listbox it forces to show all the rows for that particular month , which is normal but it also shows the previous month's value in the "Transaction Date" just because the "date" is still current month selection.
I'm sorry if this is sound confusing. Please do check the below image for more detail, it will be easy for you to understand once you have a look . I have attached the sample Qvw file too. 

[Or]

Sounds like you should be deriving the Month field from Transaction Date instead, then?

[arunqlik2view]

That's the catch, I shouldn't be doing that. I know it sounds crazy but is there a work around. I came across about canonical dates concept but I was not sure how to use in this case. some help would be great.
Please remember that we can't use Month(Transaction date) . 
Thanks